Retroverted passage type muffler with expansion chambers



Patented Sept. 15,1953

RETROVERTED PASSAGE TYPE MUFFLER WITH EXPANSION CHAMBERS Beecher B. Cary, Jackson, Mich., assignor to Hayes Industries, Inc., Jackson, Mich., a corporation of Michigan Application August Z4, 1950, Serial N o. 181,124

(Cl. ISI- 54) 1 Claim. l

The present invention relates to improvements in muillers for use on multiple cylinder, high speed, high compression engines of automobiles.

In the design of automobile muillers maximum sound attenuation over a wide operating range is desired along with restricted limitation upon the size, and shape of the muffler due to frame and body construction.

From the standpoint of minimum back pressure, straight through flow type of mufers give the best performance, However, where maximum sonud attenuation over a wide operating range is required, this type of muffler becomes of excessive length, shell noises are diicult to control and expansion and contraction problems are multiplied by the length of the component parts of the muffler.

It is the object of the present invention to provide a mulller in which the advantages of the retroverted type of construction has been combined with some of the chambering and conduit characteristics of the straight through type to provide a relative compact, structurally strong, high capacity muiller which will give substantial sound attenuation over the full operating use of the present day high speed, high compression automobile internal combustion engine with minimum back pressure. The invention is deemed to reside in details of construction and the arrangement and combination of parts.

In the accompanying drawings,

Fig. I is a vertical cross-sectional View of a muffler embodying the structural principles of the present invention, and

Fig. II is a cross-sectional view taken on line A.

II-II of Fig. I.

The outer casing I6 of the muiller is of elliptical cross-section comprising an outer sheet metal shell I2 spot welded along the lap seam I4, a layer of asbestos I6 and a double wrapped inner sheet metal shell I8 spot welded along the lap seam 20. The heads 22 and 24 are rolled upon the inner shell I8 with deformation of the inner and outer shells I2 and I8 in the manner indicated in Fig. I. The inlet and outlet tubes 26 and 28, respectively, are spot welded in flanged apertures 30 and 32 of the heads 22 and 24.

The structure for providing retroverted flow of the exhaust gases entering the inlet 26 is in the form of a unit having a slip t connection with the inner shell I8 and the inlet and outlet tubes 26 and 28. This unit comprises tubes 34 and 36 which may be of approximately the same size and length, except for the exterior portion 38 having a slip t with the inlet tube 26, and a 2 much longer tube 40 which extends practically the entire length of the muffler and has a slip iit with the outlet tube 28.

Between the heads 42 and 44 the tubes 34, 36 and 40 are perforated at 4I, preferably in the manner disclosed in U. S. Patent No. 2,070,543. Through these perforations the interior of the tube 40 is in communication with the acoustic chamber 46 defined by the shell 48 provided with longitudinal flanges 50. The flanges 50 provide structural support across the minor axis of the casing I0 with respect to inwardly directed forces only as there is a slip iit between their outer edges 52 and the interior wall of the shell I8. The flanges 50 have the further function of forming a partition along with the shell 48 for the chambers 54 and 56 with which the interiors of the tubes 34 and 36, respectively, communicate through the perforations at 4I.

The tube 36 discharges exhaust gases from the inlet tube 26 into the expansion and resonator chamber 58 defined between the head 42 and the baille 6I] with which the tube 40 has a slip fit at 62. Restricted openings 64 in the head 42 places the chamber 58 in compound arrangement with the chambers 54 and 56.

Expanded gases from the chamber 56 flow in the tube 34 in counterdirection to the gas flow in the tube 36 into the secondary expansion chamber 66 from which the expanded and sound attenuated gases are conducted by the tube 46 to the outlet 28. Further sound attenuation takes place as the gases flow through the tube 40 as a result of the embracing acoustic chamber 46 and the enlarged lower frequency chamber 68 defined between the baille 60 and the head 24. Elongated slots 10 provide communication be tween the interior of the tube 40 and the chamber 68, being preferred to the arch type of perforation 4I at this particular point.

It will be understood that where reference is made to expansion of gases such expansion will also be accompanied by a contraction of volume due to cooling which will, likewise, assist in reducing back pressures. In practice the diameter of the tube 40 may be less than the tubes 34 and 36, if desired.

Having thus described my invention what I claim as new and desire to protect by Letters Patent is:

A muler comprising an outer casing having heads at opposite ends including an inlet and an outlet, a pair of expansion chambers located in said casing, a retroverted gas flow unit disposed in said casing and located between said chambers, said unit including three tubes, one of which conducts gases from said inlet across one of said expansion chambers and discharges the gases into said other expansion chamber, another of said tubes conducting gases between said expansion chambers, and the third of said tubes conducting gases from the first of said expansion chambers across the second of said expansion chambers to said outlet, sound attenuation chambers embracing said tubes between said expansion chambers, openings defined in the Wall of said tubes within the area embraced by said sound attenuation chambers to acoustically connect the interior of said tubes with the interior of said sound attenuation chambers, a transverse wall common to and constituting one of the end walls for each of said sound attenuation chambers and also defining one of the end walls of one of said expansion chambers, and openings defined in said transverse wall to bring said last mentioned expansion chamber and said sound attenuation chambers into compound acoustic arrangement with each other through said transverse wall.

BEECHER B. CARY.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 1,964,996 Oldberg July 3, 1934 2,018,084 Oldberg Sept. 24, 1934 2,357,791 Powers Sept. 5, 1944 2,520,756 Bryant a Aug. 29, 1950V FOREIGN PATENTS Number Country Date `126,776 yAustralia. Feb. 26a, 1948A 

